| 摘要 |
PURPOSE:To enable measurement of a small atm. difference of several mm H2O, by transmitting air current generated because of the atm. difference to a mobile valve as amount of air to check the movement thereof with the detecting of the passage and interception of light. CONSTITUTION:When a atm. difference is generated with the atm. of air on the outgoing side 4 thereof being lower than that on the incoming side 2 thereof inside a cylinder 1, air starts to flow to the outgoing side 4 from the incoming side 2 to make a mobile valve 7 separate form a diaphragm 3 against a force of a spring 9 and air flow according to the atm. difference. Then, the mobile valve 7 stops in balance at a fixed position because of the atm. difference. When the movement of the mobile valve 7 exceeds a specified value, light is intercepted between light emitting and receiving sections 10 and 11 through which the light has so far passed. Then, the atm. difference can be detected as such above a set value detecting the movement of the mobile valve 7. In addition, the atm. difference set for measurement is determined as desired depending on the spring 9, the area of hollow of the diaphragm 3, the outer diameter of the mobile valve 7 and the inner diameter of the cylinder 1.
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